# Monitoring Filtered Signal in Lock-In Instrument with PID

**URL:** <https://forum.liquidinstruments.com/t/monitoring-filtered-signal-in-lock-in-instrument-with-pid/934>\
**Category:** Support & Troubleshooting\
**Created:** [April 16, 2024, 2:52pm UTC](https://forum.liquidinstruments.com/t/monitoring-filtered-signal-in-lock-in-instrument-with-pid/934 "2024-04-16T14:52:34Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![wtobias](https://avatars.discourse-cdn.com/v4/letter/w/96bed5/32.png) [@wtobias](https://forum.liquidinstruments.com/u/wtobias)\
**Post date:** [April 16, 2024, 2:52pm UTC](https://forum.liquidinstruments.com/t/monitoring-filtered-signal-in-lock-in-instrument-with-pid/934/1 "2024-04-16T14:52:34Z")

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Hi, I am using a Moku:Lab, version 3.1. In the lock-in amplifier instrument, is there a natural way to probe the demodulated and filtered signal (i.e., error signal) when the PID controller option is engaged? I have attached a screenshot showing this probe point:

 ![Moku_LockIn](https://canada1.discourse-cdn.com/flex035/uploads/liquidinstruments/original/1X/d11993fdf49963e800c944dcd642529411c9cbe1.jpeg)

I understand that I could 1. add an external PID controller using multi-instrument mode and monitor the lock-in output or 2. output a second filtered signal and monitor that, but I would prefer to use only one instrument and to save the second output for the local oscillator. Thanks!

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**Author:** ![hanklong](https://yyz1.discourse-cdn.com/flex035/user_avatar/forum.liquidinstruments.com/hanklong/32/288_2.png) [@hanklong](https://forum.liquidinstruments.com/u/hanklong)\
**Post date:** [April 16, 2024, 3:10pm UTC](https://forum.liquidinstruments.com/t/monitoring-filtered-signal-in-lock-in-instrument-with-pid/934/2 "2024-04-16T15:10:52Z")

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Hi @wtobias Will,

Thank you for posting the questions here!

Unfortunately, I am sorry that we currently don’t have the probe point before the signal entering the PID. I will make a feature request for this point. Thank you very much for your understanding and patience!

Best regards,  
Hank

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**Author:** ![wtobias](https://avatars.discourse-cdn.com/v4/letter/w/96bed5/32.png) [@wtobias](https://forum.liquidinstruments.com/u/wtobias)\
**Post date:** [April 16, 2024, 3:27pm UTC](https://forum.liquidinstruments.com/t/monitoring-filtered-signal-in-lock-in-instrument-with-pid/934/3 "2024-04-16T15:27:54Z")

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Thanks, Hank! This probe point would be very useful for monitoring the performance of the loop.